THURSDAY, Aug. 21, 2014 (HealthDay News) -- The two American health-care workers infected with the deadly Ebola virus while doing missionary medical work in West Africa have been released from the Atlanta hospital where they have been slowly recovering for several weeks, officials said Thursday.

Dr. Kent Brantly, 33, was released from Emory University Hospital Thursday morning.

Nancy Writebol left the hospital Tuesday. Her family and officials said the 59-year-old woman is still weak and continues to recuperate at an undisclosed location, the Associated Press reported.

Brantly, looking gaunt, spoke at a Thursday morning news conference where he thanked his medical team and the millions of people around the world who had prayed for him, USA Today reported. "Please do not stop praying for the people of West Africa," he said.

Emory doctors said neither Brantly nor Writebol pose a risk to the public.

Brantly called it "a miraculous day."

Brantly was working for the Christian aid group Samaritan's Purse, treating Ebola patients in Liberia when he fell ill. He and fellow aid worker Writebol were flown to Emory University Hospital in Atlanta early this month, where they were treated in an isolation unit.

Brantly and Writebol shouldn't endure long-term illness or disability because of their brush with the deadly virus, according to one of the United States' most experienced Ebola experts.

Dr. Joseph McCormick, regional dean of the University of Texas School of Public Health in Brownsville, told HealthDay that both aid workers most likely haven't endured any permanent organ damage or contracted a lasting chronic illness from the Ebola virus. And both should emerge from their struggle with immune resistance against future Ebola infection.

He said most survivors "get pretty much back to normal" over time, but admitted "this is something we know less about than we should."

McCormick is one of the very few U.S. physicians with first-hand experience with Ebola. As an officer with the U.S. Centers for Disease Control and Prevention, he belonged to the team that investigated the first Ebola epidemic in 1976, which occurred in the Congo, as well as the next two African outbreaks of Ebola.

Ebola victims who survive -- the virus kills 60 to 90 percent of those it infects -- first must deal with the loss of body mass caused by their illness, McCormick said.

"Over a period of two to three weeks, in addition to becoming physically very weak, they lose a lot of body mass," McCormick said earlier this month. "It's difficult for them to move around at all, and it takes some time for them to regain the ability to eat much."

Patients with Ebola experience terrible headaches plus body and muscle pain. "They have a tremendous sore throat, to the point where they cannot swallow their own saliva," he said.

There's not a lot that doctors could do for Brantly and Writebol, besides monitoring their vital statistics, providing pain medications, and encouraging them to eat and drink, McCormick said.

Both Brantly and Writebol received an experimental drug called Zmapp, but it's not known if the medication helped or whether they improved on their own, as can happen to some people with the disease. The treatment is so new it hasn't been tested in people, the Associated Press reported.

When both aid workers do make a full recovery, they likely will have one much-envied health advantage over most people, McCormick said -- a naturally acquired immunity to Ebola.

"They absolutely build up immune resistance," he said. "If I were out there right now running the program in West Africa, I would be looking for people who are far enough out of recovery that they feel well again. Those are the people I would be training to take care of patients, because they are the least likely to become reinfected."

The Ebola outbreak in West Africa has killed 1,350 people so far. Ebola cases have been reported in Guinea, Liberia, Sierra Leone and, to a lesser extent, Nigeria.

According to the World Health Organization (WHO), deaths are occurring most frequently in Liberia, which now accounts for at least 576 of the fatalities. Nearly 2,500 people have fallen ill across West Africa, which has now seen more infections during the current outbreak than in all of the previous two-dozen Ebola outbreaks combined, the APress reported.

Symptoms of Ebola include a sudden fever, intense weakness, muscle pain, headache and sore throat. This is followed by vomiting, diarrhea, rash, poor kidney and liver function and, in some cases, both internal and external bleeding.

Unlike diseases such as tuberculosis or flu, Ebola isn't spread by breathing air from an infected person. Transmission requires direct contact with blood, secretions, organs or other body fluids of infected living or dead persons or animals, the WHO said.